Field of the Invention
The invention relates to a circuit breaker unit for interrupting an electrical line, having a contact arrangement and having an electromagnetic drive means. The contact arrangement has a first and a second fixed contact and a guided moving contact, wherein, in this context, the expressions “contact” and “contact piece” are to be understood synonymously. The electromagnetic drive means is designed for moving the moving contact. The circuit breaker unit can assume a first state and a second state, wherein, in the first state, there is no electrical connection between the first and the second fixed contact, whereas in the second state, the moving contact electrically connects the two fixed contacts to one another. The circuit breaker unit can be transferred from the second state into the first state by movement of the moving contact.
Switching systems with the circuit breaker unit of said type are already known and generally serve, in medium-voltage and high-voltage technology, for the switching of currents, in particular short-circuit currents. They are used in particular in electrical energy supply networks, where short-circuit currents can lead firstly to a severing of the energy flow to the consumer and secondly to high mechanical loads of current-conducting network components.
In their article “Proactive Hybrid HVDC Breakers—A key innovation for reliable HVDC grids”; Integrating super grids and micro grids International Symposium, 2011, Häfner et al. describe a hybrid direct-current switching system in which the main path comprises a mechanical breaker switch and an electronic auxiliary switch. In the event of a short circuit, the rising short-circuit current is commutated by way of the auxiliary switch from the main path to a bypass path, wherein at the same time, the opening of the breaker switch is initiated. In the bypass path there is arranged a power switch unit which has a series circuit of electronic switches. If the breaker switch has reached the required dielectric strength, the short-circuit current can be interrupted by way of the power switch unit. The energy released in the process is dissipated in non-linear resistors of the power switch.
In known mechanical breaker switches of medium-voltage and high-voltage switching systems, spring store drives are normally used for the mechanical opening and closing of the contact system. The switching times that can be achieved here are limited to some 10 to 50 ms. For switching systems in high-voltage direct current transmission installations (HVDC), for example, such switching times are far too long, such that solutions with faster switching times are desirable.
The article “A DC Hybrid Circuit Breaker With Ultra-Fast Contact Opening and Integrated Gate-Commutated Thyristors (IGCTs)”; IEEE Transactions on Power Delivery, Vol. 21, No. 2, 2006 by J-M. Meyer et al. describes the mechanical circuit breaker unit of the type described in the introduction. The moving contact of the contact arrangement is in this case realized as a solid copper disk which is guided so as to be movable perpendicularly to the current flow direction. The electromagnetic drive means comprises a Thomson coil which is arranged coaxially with respect to the copper disk. Utilizing the Thomson effect, the moving contact can be moved, such that the breaker unit is transferred from the second state into the first state.
Proceeding from the prior art, it is the object of the present invention to propose an alternative circuit breaker unit of the type mentioned in the introduction.